Image reading apparatus and circuit board unit used therefor

ABSTRACT

An image reading apparatus (X) includes a light source, a case ( 2 ) for accommodating the light source, and a substrate ( 8 ) mounted to the case ( 8 ). A plurality of sensor IC chips ( 7 ) for detecting the light traveling from an image reading region are mounted on the substrate ( 8 ). The sensor IC chips ( 7 ) are arranged at positions closer to a second side edge ( 8   b ) than to a first side edge ( 8   a ) of the substrate. A predetermined wiring pattern is formed on the substrate ( 8 ). The sensor IC chips ( 7 ) are electrically connected to the wiring pattern via wires (W). The wires (W) are connected to the wiring pattern by extending from the upper surface of the sensor IC chips ( 7 ) toward the first side edge ( 8   a ) of the substrate.

TECHNICAL FIELD

The present invention relates to an image reading apparatus used forreading an image printed on a document, for example. The presentinvention also relates to a circuit board unit used for manufacturing animage reading apparatus.

BACKGROUND ART

FIG. 6 of the present application shows an example of prior-art imagereading apparatus. The illustrated image reading apparatus includes asubstrate 100, and a case 200 to which the substrate is mounted. Thesubstrate has a rectangular configuration elongated in a directionperpendicular to the sheet surface of the figure. The substrate 100 hasan upper surface on which a plurality of light sources 101 and aplurality of sensor IC chips 102 are mounted. The light sources 101 arealigned along a first side edge 100 a of the substrate 100 withpredetermined intervals. The sensor IC chips 102 aligned along a secondside edge 100 b of the substrate 100. Each of the sensor IC chips 102has an upper surface formed with a light receiving portion 102 a.

The case 200 is formed with a light path 201 for guiding the lightemitted from the light sources 101 to an image reading region S. A lensarray comprising a plurality of lenses 105 is disposed below the imagereading region S. The light reflected by the image reading region S isconverged by the lenses 105 and received by the light receiving portion102 a of each sensor IC chip 102.

Each sensor IC chip 102 has the photoelectric conversion function andoutputs an image signal of the level corresponding to the receivedamount of light. To obtain an image signal faithful to the object to beread, the light emitted from the light sources 101 need be preventedfrom directly reaching the light receiving portion 102 a. For thispurpose, a partition wall 202 is provided between the light sources 101and the sensor IC chips 102. The partition wall 202 engages the uppersurface of the substrate 100 and extends in the longitudinal directionof the substrate 100.

As indicated by double-dashed lines in FIG. 6, a connector 103 forexternal connection is attached to the substrate 100. The connector 103is connected to a wiring pattern (not shown) formed on the upper surfaceof the substrate 100. The wiring pattern is connected to the lightsources 101 and the sensor IC chips 102. Such an image reading apparatusis disclosed in JP-A 2001-339574, for example.

In the image reading apparatus of FIG. 6, the wiring pattern isconnected to each IC chip 102 via a wire W. Specifically, the upper endof the wire W is connected to the IC chip 102, whereas the lower end ofthe wire is connected to the wiring pattern.

The prior-art structure has the following drawbacks. As shown in FIG. 6,the lower end of the wire W is connected to the wiring pattern on theright side of the chip 102 (adjacent the second side edge 100 b). Withsuch an arrangement, in mounting the substrate 100 to the case 200, theoperator's hand or the case 200 is likely to come into contact with thewire W. When such contact occurs, the wire W may be broken or theconnection between the wire W and the chip 102 or the wiring pattern mayfail.

DISCLOSURE OF THE INVENTION

The present invention is conceived under such circumstances. It is,therefore, an object of the present invention to provide an imagereading apparatus in which improper external force is not exerted to thewires connecting the wiring pattern and the sensor IC chips on thesubstrate to each other. Another object of the present invention is toprovide a circuit board unit used for manufacturing such an imagereading apparatus.

According to a first aspect of the present invention, there is providedan image reading apparatus comprising: a light source for illuminatingan image reading region extending in a primary scanning direction; acase for accommodating the light source; a substrate including a firstside edge and a second side edge spaced from each other in a secondaryscanning direction which is perpendicular to the primary scanningdirection, the substrate being mounted to the case; a plurality ofsensor IC chips for detecting light traveling from the image readingregion, the sensor IC chips being mounted on a principal surface of thesubstrate at positions closer to the second side edge than to the firstside edge; a wiring pattern formed on the substrate; and a plurality ofwires electrically connecting the sensor IC chips and the wiring patternto each other. Each of the wires is connected to the wiring pattern byextending from a corresponding one of the sensor IC chips toward thefirst side edge of the substrate.

Preferably, the image reading apparatus of the present invention furthercomprises a light guide for guiding the light emitted from the lightsource to the image reading region. The case is provided with apartition wall for separating the light guide and the sensor IC chips,and the partition wall is spaced from the substrate.

Preferably, the light guide is made of transparent resin.

Preferably, the partition wall includes a flat surface extendingparallel to the principal surface of the substrate, and the wires enterbetween the flat surface and the principal surface of the substrate atleast partially.

Preferably, the image reading apparatus of the present invention furthercomprises a reflector held in contact with the light guide to preventlight from leaking from the light guide. The reflector is provided onthe partition wall.

Preferably, the plurality of sensor IC chips are arranged in a straightrow. The wiring pattern includes a conductive path which extends acrossthe row of the sensor IC chips and a conductive path which does notextend across the row of the sensor IC chips.

Preferably, each of the sensor IC chips is provided with a plurality ofconnection pads, and a plurality of light receiving portions arranged ina straight row. The connection pads are arranged at positions offsettoward the first side edge of the substrate with respect to the lightreceiving portions.

Preferably, the image reading apparatus of the present invention furthercomprises a connector for external connection attached to the first sideedge of the substrate. The connector is electrically connected to thewiring pattern.

According to a second aspect of the present invention, there is provideda circuit board unit comprising: a substrate including a first side edgeand a second side edge spaced from each other; a plurality of sensor ICchips mounted on the substrate at positions closer to the second edgethan to the first edge; a wiring pattern formed on the substrate; and aplurality of wires electrically connecting the sensor IC chips and thewiring pattern to each other. Each of the wires is connected to thewiring pattern by extending from a corresponding one of the sensor ICchips toward the first side edge of the substrate.

Preferably, each of the sensor IC chips is provided with a plurality ofconnection pads, and a plurality of light receiving portions arranged ina straight row. The connection pads are arranged at positions offsettoward the first side edge of the substrate with respect to the lightreceiving portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing main structural parts ofan image reading apparatus according to the present invention.

FIG. 2 is a sectional view showing the state in which the mainstructural parts are assembled together.

FIG. 3 is a sectional view taken along lines III-III in FIG. 2.

FIG. 4 is a sectional view take along lines IV-IV in FIG. 2.

FIG. 5 is a plan view showing a wiring pattern of a circuit board unitaccording to the present invention.

FIG. 6 is a sectional view showing the structure of a prior-art imagereading apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin detail with reference to the accompanying drawings.

FIGS. 1 through 4 show an example of image reading apparatus accordingto the present invention. As will be understood from FIG. 1, the imagereading apparatus X includes a case 2, a light guide 3, a reflector 4, atransparent plate 5, a lens array 6 and a circuit board unit U. The unitU includes a rectangular substrate 8 elongated in the primary scanningdirection (See the arrow A in FIG. 1), and various elements (which willbe described later) provided on the substrate.

The substrate 8 has a principal surface (upper surface) 81 on which alight source unit 1 and a plurality of sensor IC chips 7 are mounted.The substrate 8 includes two side edges extending in the primaryscanning direction, i.e., a first side edge 8 a and a second side edge 8b.

The light source unit 1 serves to illuminate an image reading region S(See FIG. 3). In the illustrated example, the light source unit 1comprises three kinds of light emitting diodes, i.e., a red diode, agreen diode and a blue diode (See FIG. 4). As shown in FIG. 1, the lightsource unit 1 is provided at an end of the substrate 8. Further, asshown in FIG. 4, the light source unit 4 is close to the first side edge8 a than to the second side edge 8 b.

The case 2 is made of a synthetic resin and has a lower surface on whichthe substrate 8 is mounted. As shown in FIG. 2, the case 2 includes afirst space 21 for accommodating the light source unit 1. As shown inFIGS. 2-4, the case 2 further includes a second space 22 foraccommodating the sensor IC chips 7, and a third space 23 foraccommodating the light guide 3 and the reflector 4. The first space 21and the second space 22 are separated by a first partition wall 24 ofthe case 2 (See FIG. 2). The second space 22 and the third space 23 areseparated by a second partition wall 25 (See FIGS. 2 and 3). The secondpartition wall 25 is spaced from the substrate 8 and provided above thesubstrate. The first and the second partition walls 24 and 25 areprovided to block the light directly traveling toward the sensor ICchips 7 from the light source unit 1. As shown in FIG. 3, the secondpartition wall 25 has a flat surface 25 a extending parallel to theprincipal surface 81 of the substrate 8. The wire W enters between theflat surface 25 a and the principal surface 81 of the substrate 8 atleast partially.

The light guide 3 is transparent and may be made of polymethylmethacrylate (PMMA), for example. As shown in FIG. 2, the light guide 3extends in the longitudinal direction of the case 2 and includes anauxiliary portion 31 and a main portion 32. The auxiliary portion 31 hasa light incident surface 31 a facing the light source unit 1. The lightimpinging on the light incident surface 31 a travels through theauxiliary portion 31 to enter the main portion 32. As shown in thefigure, the light traveling through the main portion 32 is totallyreflected by the surfaces of the main portion 32. The lower surface ofthe main portion 32 is formed with a plurality of recesses (not shown)arranged with predetermined intervals. The light traveling through themain portion 21 is scattered and reflected by the recesses and partiallyemitted toward the image reading region S through a light emissionsurface 32 a (See FIG. 3). The image reading region S is irradiated withthe emitted light.

The reflector 4 is made of a synthetic resin and is made white toincrease the light reflectance. The reflector 4 includes anaccommodation portion 41 for accommodating the light guide 3. Thereflector 4 covers the light guide 3 except the light incident surface31 a and the light emission surface 32 a to prevent the waste of lightdue to leaking from the light guide 3. As shown in FIGS. 2 and 3, thereflector 4 is disposed on the second partition wall 25.

The transparent plate 5 is made of a synthetic resin or glass andmounted on the upper surface of the case 2. The transparent plate 5comes into contact with the document D which slides thereon by thetransfer by the platen roller P in the secondary scanning direction (thedirection indicated by the arrow B in FIGS. 3 and 4). The secondaryscanning direction is perpendicular to the primary scanning direction.

As shown in FIGS. 3 and 4, the lens array 6 is arranged between thesecond space 22 and the third space 23 of the case 2. The lens array 6includes a holder 61 made of a synthetic resin and extending in theprimary scanning direction, and a plurality of lenses 62 held by theholder. The above-described image reading region S is located directlyabove the lenses 62 and on the upper surface of the transparent plate 5.

As shown in FIG. 5, each of the sensor IC chips 7 comprises an elongatedrectangular semiconductor device. The plurality of sensor IC chips 7 arealigned in the longitudinal direction of the substrate 8. The sensor ICchips 7 are located closer to the second side edge 8 b than to the firstside edge 8 a. Therefore, with the sensor IC chips 7 serving as theboundary, the upper surface 81 of the substrate 8 is partitioned intotwo regions of different widths, i.e., a first region 81 a and a secondregion 81 b. As will be understood from the figure, the first region 81a is located on the side of the first side edge 8 a of the substrate andis larger in area (width) than the second region 81 b (located on theside of the second side edge 8 b).

Each of the sensor IC chips 7 has a plurality of light receivingportions 71. The light receiving portions receive light passed throughthe lens array 6. The sensor IC chip 7 has the photoelectric conversionfunction and outputs an image signal of an output level corresponding tothe received amount of light.

As shown in FIG. 5, a plurality of conductive pads 72 are provided onthe upper surface of the sensor IC chip 7. The pads 72 are arranged atpositions offset toward the first side edge 8 a with respect to thecenter of the sensor IC chip 7 in the width direction (verticaldirection in FIG. 5). These pads 72 include pads 72 (Vcc, VREF) forvoltage application, a pad 72 (GND) for ground connection and pads 72(CLK, SI, SP, AO, SO) for inputting or outputting various kinds ofsignals. In the sensor IC chip 7, when a serial-in-signal is inputtedinto the pad 72 (SI), the charge stored in the light receiving portions71 is discharged. The discharged charge is serially outputted from thepad 72 (AO).

The substrate 8 is made of e.g. a ceramic material, and a connector 10for external connection is attached to the first side edge 8 a (See FIG.1). The connector 10 is electrically connected to the light source unit1 and the sensor IC chips 7 through a wiring pattern 9. The wiringpattern 9 comprises a plurality of conductive paths corresponding to thepads 72. Each of the conductive paths is connected to the correspondingpad 72 via a wire W. The upper end of each wire W is connected to thecorresponding pad, whereas the lower end of the wire is connected to thecorresponding conductive path. The connection point between the lowerend of the wire W and the conductive path is located in the first region81 a. Thus, all the wires S are connected to the wiring pattern 9 byextending from the corresponding pads 72 toward the first side edge 8 a.The conductive paths for the pads 72 (GND, AO, VREF) extend in both ofthe first region 81 a and the second region 81 b. Therefore, theconductive paths for the pads GND, AO and VREF extend across the chip 7below the sensor IC chip 7. The conductive paths for other pads 72 (Vcc,CLK, SI, SP, SO) are provided in the first region 81 a and do not extendinto the second region 81 b. (Although these conductive paths arepartially located below the chip 7, the paths do not extend into thesecond region 81 b.)

As described above, in the image reading apparatus X of the presentinvention, the wires W extend from the sensor IC chip 7 toward the firstside edge 8 a. Therefore, in mounting the substrate 8 to the case 2, theoperator's hand does not come into contact with the wires W. Further, asshown in FIG. 3, the second partition wall 25 of the case 2 is spacedfrom the substrate 1 and provided above the substrate, so that thecontact between the wires W and the case 2 can be avoided. With such astructure, the prior-art problems such as the breakage of wires W or theconnection failure can be solved. Moreover, in the example shown in FIG.3, the case 2 includes an inclined wall surface 2 a facing the sensor ICchips 7. The wall surface 2 a extends in a direction perpendicular tothe sheet surface of the figure. With such an arrangement, the contactbetween the case 2 and the chips 7 can be avoided.

Further, in the image reading apparatus X, the wires W extend from thesensor IC chip 7 to the side of the first side edge 8 a and connected tothe wiring pattern 9 in the first region 81 a. With such a structure, atleast part of the conductive paths connected to the sensor IC chip 7 isonly required to be formed at the first region 81 a. As a result, thestructure of the wiring pattern 9 can be made simpler than the prior-artwiring pattern, whereby the manufacturing cost can be reduced.

The present invention being thus described, it is apparent that the samemay be varied in many ways. Such variations should not be regarded as adeparture from the spirit and scope of the present invention, and allsuch modifications as would be obvious to those skilled in the art areintended to be included within the scope of the following claims.

1. An image reading apparatus comprising: a light source for illuminating an image reading region extending in a primary scanning direction; a case for accommodating the light source; a substrate including a first side edge and a second side edge spaced from each other in a secondary scanning direction which is perpendicular to the primary scanning direction, the substrate being elongated in the primary scanning direction and mounted to the case; a plurality of sensor IC chips for detecting light traveling from the image reading region, the sensor IC chips being mounted on a principal surface of the substrate at positions closer to the second side edge than to the first side edge; a wiring pattern formed on the substrate; a plurality of wires electrically connecting the sensor IC chips and the wiring pattern to each other; a light guide for guiding light emitted from the light source to the image reading region; and a reflector held in contact with the light guide to prevent light from leaking from the light guide; wherein each of the wires is connected to the wiring pattern by extending from a corresponding one of the sensor IC chips toward the first side edge of the substrate, the light source is mounted on an end of the principal surface of the substrate in the primary scanning direction, the case is provided with a first partition wall for separating the light source and the sensor IC chips and with a second partition wall for separating the light guide and the sensor IC chips, the first partition wall is held in contact with the principal surface of the substrate, and the second partition wall is spaced from the substrate, and the reflector is provided on the second partition wall.
 2. The apparatus according to claim 1, wherein the light guide is made of transparent resin.
 3. The apparatus according to claim 1, wherein the second partition wall includes a flat surface extending parallel to the principal surface of the substrate, and wherein the wires enter between the flat surface and the principal surface of the substrate at least partially.
 4. The apparatus according to claim 1, wherein the plurality of sensor IC chips are arranged in a straight row, and wherein the wiring pattern includes a conductive path which extends across the row of the sensor IC chips and a conductive path which does not extend across the row of the sensor IC chips.
 5. The apparatus according to claim 1, wherein each of the sensor IC chips is provided with a plurality of connection pads, and a plurality of light receiving portions arranged in a straight row, and wherein the connection pads are arranged at positions offset toward the first side edge of the substrate with respect to the light receiving portions.
 6. The apparatus according to claim 1, further comprising a connector for external connection attached to the first side edge of the substrate, wherein the connector is electrically connected to the wiring pattern.
 7. The apparatus according to claim 1, wherein the light source comprises a light emitting diode provided on the principal surface of the substrate at a position closer to the first side edge than to the second side edge. 